Pinch valves typically pinch a rubber or elastic sleeve mounted in a fluid conduit system to control flow, completely or partially blocking flow. The sleeve of such valves usually has flanges at each end of the center pinch section. Examples of such sleeves with end flanges are seen, for example, in U.S. Pat. Nos. 3,268,201, 3,771,758, 3,724,807, 4,172,980, 4,322,054, 4,372,528, 4,492,253 and 4,523,738.
Such flanges serve typically as the gasket sealing each end of the sleeve in a typical flange connection high pressure pipe system. The sleeve flanges are compressed between the standard metal pipe flange on the exterior and an interior metal flange with clamp fasteners passing between the metal flanges and through the sleeve flange. The interior metal flange is usually on the end of the metal valve housing surrounding the sleeve, whether the valve be mechanically or fluid operated.
This mounting system has several major drawbacks. After the sleeve is constructed, in order to test the sleeve, the internal flange must be provided which is usually only provided by building the valve housing around the sleeve and then installing the valve in the flanged connections of the system. If the sleeve is then faulty, this can be a time consuming and expensive proposition. In other words, one usually can't otherwise test the sleeve.
This is particularly true with air operated valves since one usually can't make a seal without installation, or some very expensive jury rig testing machine. Even so, the sleeve flanges still have to be positioned between pipe flanges and compressed.
Accordingly, it would be advantageous to have a sleeve for such valves which could easily be rigged for testing without complete construction and installation of the valve.
Another disadvantage of such construction is when the sleeve flange is sufficiently compressed to make the required seal, the interior of the sleeve will bulge slightly inwardly and create a protrusion into, or restriction in the flow path where none is wanted. Although some protrusions are intentional for certain flow or pressure characteristics as seen in U.S. Pat. No. 4,372,528, unintentional restrictions are not desirable, particularly where the medium controlled is a slurry which would tend to abrade the sleeve.
Also, the sleeve flange is often used as the anchor location for belts or reinforcement extending through the center pinch section. The containment of such belt or reinforcement ends, or even special anchors as seen in prior U.S. Pat. No. 4,523,738, compromises the function of the flange as a sealing gasket, and vice versa.
The sleeve flange, in part because of its containment of belts, reinforcements or anchors isn't usually suitable for connection with more than one type of pipe flanging. For example, the most common pipe flangings used are flat faced and raised face. A raised face flange connection includes a slightly raised ring on one flange face which telescopes into a socket on the mating flange face. Using a conventional pinch sleeve flange for both types of connection may result in a poor connection and/or damage to the sleeve contributing to early failure and shortening the useful life of the sleeve. Although it is possible to use additional gasketing or to design the sleeve flange for a specific type of system pipe flanging, this creates multiple economic problems.
Accordingly, it would be desirable to have a pinch valve which can readily be incorporated in a system without regard to the type of system pipe flanging, without additional gaskets, without compromising the pinch section reinforcement, and without creating bulges, protrusions or distortions in the flow path, particularly at the valve ports.
The use of such belts and reinforcements which extend into the sleeve flanges creates a number of design problems for such pinch or control valves. The fabric used for such belts or reinforcements must normally stretch 15 to 20% to achieve complete and proper closure of the valve. This stretching or tension creates wear points at the root of the flanges since the fabric wants to pull inwardly or toward the center as it goes around the corner at the root of the flange. To avoid this problem, pinch sleeve sections are normally longer than they would otherwise be since the longer the pinch section, the less stretch is required to achieve proper closure. While this may somewhat obviate the corner wear problem, it creates a pinch control valve which is longer than the ANSI (American National Standards Institute) standards for a comparable gate valve. This is particularly true for larger size valves. This then means that special fabrication and sections are required to incorporate a pinch control valve into a system. Such systems are considerably less expensive to design and erect if standard parts and lengths can be used. The lack of adherence to ANSI standards can mean the selection of a less efficient or effective valve solely for cost considerations.
It would accordingly be desirable to have a reinforced pinch valve sleeve where the stretch or tension problem is avoided not only avoiding the wear problems encountered, but also enabling the center pinch section to be shorter than normal so that the overall size of the sleeve and valve matches the ANSI standards for comparable gate valves.